Guide to square welding nuts, flange welding nuts, knurled nuts, and custom special nuts. Manufacturing processes and application guidance for specialized fastening.
Square Welding Nuts and Flange Welding Nuts
Square welding nuts (DIN 928) are designed to be resistance-welded to sheet metal or structural steel surfaces, creating a permanent threaded anchor point where only one side of the母材 is accessible. The square body shape prevents rotation during welding (weld spots are applied at each corner of the square). Flange welding nuts (DIN 929) have a hexagonal flange with welding projections (smallbumps on the underside) that concentrate the welding current for faster, more consistent welds. Hex nuts for embedded plate welding are installed in concrete or masonry during construction (embedded plates grouted into walls) with the nut accessible for later bolt installation. Available in carbon steel (zinc-plated or HDG) and stainless steel (304/316). Our factory wholesale stock includes common sizes M6 through M16.
Knurled Nuts, Step Nuts and Custom Special Nuts
Knurled round nuts have diamond or straight knurling on the outer diameter for finger-grip tightening—commonly used on camera tripods, machinery adjustment mechanisms, and hand-tightened collar applications. Step shape special nuts (step nuts or reduced-body nuts) have multiple diameter sections, allowing them to fit through different sized holes in an assembly while threading onto different母材 thicknesses. Custom special nut processing includes: left-hand thread nuts (for reverserotation applications), drill-down nuts (with integral drill tip for one-step installation into concrete), and PEM nuts (press-fit nuts for sheet metal). Minimum order quantities for custom non-standard nuts start at 1,000 pieces, with samples available in 10-15 working days.
Fine Thread Round Lock Nuts: Custom Manufacturing
Fine thread round lock nuts with custom specifications (DIN 980 / ISO 16032 all-metal lock nuts, or DIN 929 flange weld nuts) are available on custom order for precision applications. Common custom specifications: non-standard fine threads (M10×1.0, M12×1.25, etc.), left-hand thread (all sizes), and special materials (Brass, Bronze, Titanium). For fine thread round lock nut matching a fine thread bolt (such as UNF or metric fine), always specify both the thread size AND the nut height class (standard or heavy). Custom manufacturing typically requires 3D CAD files or detailed engineering drawings. Our engineering team can reverse-engineer from samples or sketches.
Matching Nuts for 10.9 Grade Bolts
When specifying matching nuts for 10.9 grade bolts, the minimum nut requirement is Grade 10 (proof load stress 1000 MPa). For structural applications per EN 14399, the specified nut grade must be confirmed with the bolt grade. Heavy hex nuts (DIN 6925) in Grade 10 are preferred for structural connections because the increased bearing area prevents母材 crushing. Extra large size heavy duty hex nuts for M36-M72 bolts must be specified with the thread class (6H for metric) and the coating/palte specification. For offshore or marine environments, specify A4-80 (316 stainless) nuts with 10.9 HDG bolts to avoid galvanic corrosion—never use stainless nuts with HDG bolts in seawater unless isolated.
Frequently Asked Questions
What is the weld projection on flange welding nuts?
Flange welding nuts (DIN 929) have 3-4 smallbumps (projections) on the underside of the flange that concentrate resistance welding current, ensuring fast, strong welds at lower current.
Can I weld a standard hex nut directly to steel?
Standard hex nuts are not designed for welding—the steel composition and geometry are not optimized for weld strength. Use dedicated square welding nuts (DIN 928) or flange welding nuts (DIN 929).
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